Here is the full list of all 50 Spec Ops: The Line achievements. It takes around 15-20 hours to unlock all of the achievements on Windows.
Live and let die.
Complete game on "FUBAR" difficulty.
Live and let live.
Carry on, soldier.
Choose restraint.
Kill 50 enemies using only the Attack Command. (campaign only)
Recover all Intel Items.
Save a bullet.
Kill 10 enemies while they use zip lines or are rappelling. (campaign only)
Blow up 10 explosive objects, killing at least one enemy each time. (campaign only)
Follow your orders.
Kill 50 enemies with any sniper rifle. (campaign only)
Recover 12 Intel Items.
Kill 50 enemies with grenades. (campaign only)
Play it smart.
Kill an enemy by tagging him with a sticky grenade. (campaign only)
Complete any chapter with 60%+ accuracy without dying or reloading a checkpoint.
Kill 75 enemies with any shotgun. (campaign only)
Kill 4 enemies with a shotgun in 10 seconds or less. (campaign only)
Kill 5 enemies using blind fire. (campaign only)
Sprint into cover 10 times while under fire. (campaign only)
Hit 10 enemies with your melee attack. (campaign only)
Stun an enemy by dumping sand on their head. (campaign only)
Complete game on "Walk on the Beach" difficulty.
Complete game on "Combat Op" difficulty.
Complete game on "Suicide Mission" difficulty.
You are relieved.
The end of the line.
Kill 350 enemies with any rifle. (campaign only)
Choose vengeance.
Kill 250 enemies with headshots. (campaign only)
Get out of here!
Stand united.
Kick an enemy by vaulting over a cover. (campaign only)
Show mercy.
Kill 150 enemies with any heavy weapon. (campaign only)
Buck the chain of command.
Complete three chapters in a row without being killed or reloading a checkpoint.
Play it loose.
Kill an enemy just as they are throwing a grenade. (campaign only)
Face the horrors of war.
Kill 100 enemies with any pistol or SMG. (campaign only)
Kill an Edged Weapon Expert while he is up to 5 meters away. (campaign only)
Kill 3 enemies with a single grenade. (campaign only)
Engineer an exit strategy.
We have contact.
Recover one Intel Item.
Look out below.
What's lost is found.
Kill an oryx. (campaign only)